The invention relates to a method for measuring the porosity of an element by means of a device comprising:                a measuring chamber in which the element is disposed,        a solvent tank associated with an adsorption valve, arranged between the solvent tank and an inlet of the chamber,        a pump associated with a desorption valve, arranged between an outlet of the chamber and the pump,        a pressure sensor,        control means for controlling the adsorption and desorption valves,the measuring method comprising measurement of the pressure in the chamber by means of the pressure sensor and a measuring cycle for measuring the porosity by ellipsometry, at different predetermined pressure or temperature values.        
The invention also relates to a device implementing one such method.